Japan's Nuclear Regulation Authority on Wednesday raised the severity rating of the radioactive water leak from storage tanks at the Fukushima nuclear power plant to Level 3 on the International Nuclear and Radiological Event Scale.
Level 3 of seven signifies a "serious incident." The disaster at the Fukushima power plant itself was rated as Level 7 ("major accident"), but the contaminated water leak is being treated as a separate problem.
Tokyo Electric Power reported that 0.12 tons of contaminated water leaked from a storage tank on Aug. 19, which the NRA provisionally rated as Level 1 ("deviation").
But a follow-up inspection found that the leak from that tank alone amounted to 300 tons, with traces of leaks from two other tanks as well. It also found that the leaks had started at least a month earlier. The dose of radiation for staff working near the storage tanks suddenly increased a month ago probably due to the radioactive leaks.
The NRA said IAEA measurements show the total amount of radioactive materials in the 300 tons of leaked contaminated water at the Fukushima plant to be equivalent to thousands of tera-becquerels. The leaked water is particularly highly contaminated because it was used as reactor coolant.
Meanwhile, the Japanese government finally delivered data on the radioactive leaks to the Korean Embassy in Tokyo on Tuesday. The 100-page document comes in response to a request from Seoul as long ago as Aug. 14. Tokyo also promised to deliver additional data soon.